The process of the invention pertains to the field of planar integrated optical component technologies and can advantageously be applied to the manufacturing of components used for optical fiber sensors (Reference #1: W. C. Gross et al, Applied Optics, Vol. 19, #6, page 852-858, 198) and for wide band microwave signal processing (Reference #3: T. Sueta and M. Izutsu, IEEE Trans on microwave Theory and Techniques, Vol. 38, #5, page 477-482, May 1990).
It is a known fact that previously the manufacturing of channel optical guides when in particular meant for phase modulators based upon lithium niobate electro-optical effects, suffered from the following drawbacks:
complexity of the manufacturing process, PA1 constancy of the electro-optical characteristics of the material within which the optical guide is manufactured (Reference #4: R. A. Becker, Appl. Phys. Lett., vol. 43, page 131-133, 1983). PA1 simplification of the manufacturing process, PA1 no modification of the electro-optical efficiency, and PA1 elimination of the electro-optical instability characteristics.
elimination of the optical and electro-optical characteristics of the device (Reference #5: J. L. Jackel and C. E. Rice, "Proceedings of Guided Wave Optoelectronic Material", SPIE vol. 460, page 43-48, 1984).
The manufacturing of LiNbO.sub.3 channel optical guides most commonly uses the diffusion of titanium into the lithium niobate crystal (Ref. #6: W. K. Burns et al., J. Appl. Phis., Vol. 50, #10; [page 6175-6182, Oct. 1979) and of the following deposition of a dielectric film followed by the deposition and definition of the metal electrodes.
This process is costly in terms of deposition and definition of the titanium film (complex high accuracy equipment being required to determine the thickness of the film) and of the following thermal diffusion of titanium into the crystal (temperature control at about 1000.degree. C.).
The proton exchange in acid solution between Li (li+O) of the crystal and the solution protons (H+) (has made it possible to cut the complexity of the manufacturing process to a very large degree (REF. #7: K. K. Wong, Spie, Vol. 993 "Integrated Optical Circuit Eng VI" page 13-25, 1988), but had the drawback of a reduced electro-optical efficiency of the devices. Eventually, the presence of the dielectric film above the optical guide, independently from its manufacturing process, gives rise to an instability of the modulator electro-optical characteristics. To eliminate this effect, the dielectric film must be removed above the optical guide (Ref #8: Yamada et al, Japan J. Appl. Phys. vol. 20, #4, page 733-737, Apr. 1981).